Dipole augmented slot radiating elements

ABSTRACT

The apparatus of the present invention enhances the performance of slot radiating elements or arrays, increasing the overall antenna gain, increasing the front to back signal ratio, suppressing undesirable side lobes and reducing the mutual coupling between array elements. This enhanced performance is generally achieved by augmenting the respective individual slots with exterior feed lines which form a transmission line transition to either free space or one or more dipole auxiliary radiating elements. The exterior elements can assume a number of configurations.

United States Patent 2,5 l0,290 (SH 950 Masters Inventors Appl. No.

Filed Patented Assignee Woodrow W. Black Los Angels;

Alvin Clavin, Calabasas, both of, Calif.

Apr. 2, 1969 July 20, 197 1 Hughes Aircraft Company Culver City, Calif.

DIPOLE AUGMENTED SLOT RADlATlNG ELEMENTS ll Claims, 7 Drawing Figs.

U.S. Cl

lnt.Cl [50] FieldolSearch References Cited UNITED STATES PATENTS2,573,461 10/1951 Lindenblad 343/770 2,573,746 ll/l95l Watson et 343/7712,635,189 4/l953 Van Atta l 343/767 X 3,083,362 3/1963 Stavis 343/771 UXPrimary ExaminerRodney D. Bennett, Jr. Assistant ExaminerRichard E.Berger Attorneyslames K. Haskell and Robert H. l-limes ABSTRACT: Theapparatus of the present invention enhances the performance of slotradiating elements or arrays, increasing the overall antenna gain,increasing the front to back signal ratio, suppressing undesirable sidelobes and reducing the mutual coupling between array elements. Thisenhanced performance is generally achieved by augmenting the respectiveindividual slots with exterior feed lines which form a transmission linetransition to either free space or one or more dipole auxiliaryradiating elements. The exterior elements can assume a number ofconfigurations.

PATENTED JULZO I97! SHEET 1 BF 2 Fig.1.

Fig.4.

C m B W W O r d O O W Alvin Clovm,

INVENTORS Pal-Mi 9 ATTORNEY.

PATENTEnJuLzmsrs SHEET 2 OF 2 3,594,806

Woodrow W. Black Alvin Clovin,

INVENTORS.

9. 1 o m l wl Wmll lmm l law I lm ll low! 1 mm mw Q m tm 9. R E U UATTORNEY.

DIPOLE AUGMENTEI) SLOT RADIA'II'ING ELEMENTS BACKGROUND OF THE INVENTIONIn contemporary slot arrays, interior posts or irises are often employedin conjunction with arrays of slot radiators. Such devices balance theenergy radiated from the respective slots and serve to minimizecross-polarization. In other cases where dipole radiating elements arefed by means of waveguide, a direct coupling is used from the waveguideto the respective dipole elements.

SUMMARY OF THE INVENTION In accordance with the present invention,apparatus is provided for increasing the gain of a slot array,increasing the front to back signal ratio of the array, suppressingundesirable side lobes, and reducing mutual coupling between arrayelements. In a first embodiment these features are achieved bymechanically mounting conductive posts on both sides of and electricallycoupled to the respective slots of the array. In general, the posts areone-quarter of one wavelength in height and have a diameter comparableto the width of the respective slots. Further, the pair of postsstraddling a slot forms a twin lead transmission line to improve thetransition to free space. In alternate embodiments, the transmissionlines are connected to one or more stacked dipoles. In still otherembodiments, the pairs of posts straddling the respective slots .arecurved or slanted outwards from each other, thereby separating the outerends more than the base of the posts at the plane of the slots.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a perspective view of acolumn of longitudinal slots in the broad wall of waveguide augmentedwith conductive posts;

FIG. 2 shows a perspective view of a segment of waveguide with alongitudinal slot in the broad wall augmented with posts connected to asingle dipole over each slot;

FIG. 3 shows a perspective view of a segment of waveguide with alongitudinal slot in the broad wall augmented with posts connected tostacked dipoles over each slot,

FIG. 4 shows a perspective view of a segment of waveguide with alongitudinal slot in the broad wall thereof augmented with posts whichcurve away from each other in receding from the plane of the slots;

FIGS. 5A and 5B show perspective views of segments of waveguide withlongitudinal slots in the respective broad walls thereof augmented withposts which slant outwards from each other from the plane of the slots;and

FIG. 6 shows a top view of a dipole augmented linear array of slotradiators.

Referring to FIG. I of the drawings, there is shown a seg ment 10 of atwo-dimensional planar array of post augmented slot radiators. Inparticular, segment I0 includes rectangular waveguide segments 11, I2,13, I4, with longitudinal slots 16, I7, 18, I9, 20, respectively, in thebroad wall thereof. The longitudinal slots 16-20 may be offset in acommon direction from the center of the waveguide to effect radiation ofelectromagnetic energy in the fundamental mode therein from therespective waveguide segments I I IS. Alternatively, the longitudinalslots 16-20 may be centered in the broad wall of the waveguide segments"-15, respectively, in which case addi- In operation, waveguide segmentsIl-I5 are energized in accordance with the overall phasing of the planararray of which segment I0 is a part. Microwave energy radiated fromlongitudinal slot 16 electrically couples to conductive posts 2I, 22.Similarly, microwave energy radiated from slots 17, I8, 19, 20electrically couples to conductive posts 22, 23; 23, 24; 24, 25; and 25,26, respectively. In the case of a single longitudinal slot 16, I7, I8,19 or 20 with its associated conductive posts 21-26, the element E-planepattern is approximately the same as the element I-I-plane patternwhereby the overall element pattern is substantially independent of theangle in the plane of the slot 116, 17, 18, 119 or 20. In addition,radiated energy falls off rapidly as the angle from the normal to theplane of the slot 16, I7, 18, I9 or 20 increases, thereby enhancing thegain, decreasing the mutual coupling between slots 16-20 and reducingthe side lobes.

Referring to F IG. 2 there is shown a single radiating element 30including a segment of rectangular waveguide 31 having a longitudinalslot 32 in a broad wall thereof that is displaced from the centerline toeffect radiation of electromagnetic energy in the fundamental modetherefrom. Alternatively, as specified in connection with FIG. I, thelongitudinal slot 32 may be centered and irises or other structure (notshown) used internally within the waveguide segment 31 to effectradiation. In the present case conductive posts 33, 34 of the order ofone-quarter wavelength in height and of a diameter equal to the width ofslot 32 are mounted in the E-plane on opposite sides of and midway alongthe slot 32. In addition, flat conductive elements 35, 36, one-quarterwavelength long, are mounted in the E-plane on top of and extendingoutwards from the posts 33, 34, respectively, to provide a dipole overthe slot 32 that is electrically coupled thereto by a twin leadtransmission line about one-quarter of one wavelength long formed by theposts 33, 34.

Referring to FIG. 3 there is shown an embodiment of the single radiatingelement of FIG. 2 with an additional dipole stacked in the E-plane abovethe dipole formed by onequarter wave elements 35, 36. In particular,conductive posts 37, 38 of a height equal to one-quarter wavelength aremechanically mounted directly over the posts 33, 34, on top of theone-quarter wavelength elements 35, 36, respectively. In addition, flatconductive elements 39, 40 are mounted on the posts 37, 38,respectively, directly over the elements 35, 36, as viewed in thedrawing. The stacked dipoles 35, 36 and 39, 40 enchance the directionaleffect of the single dipole 35, 36, in the radiating element of FIG. 2.

Referring to FIG. 4 there is shown a single slot radiating element 42including a rectangular waveguide segment 43 with a longitudinal slot 44in a broad wall thereof adapted to radiate electromagnetic energy fromthe waveguide segment 43. In this embodiment, curved posts 45, 46 aredisposed in the E- plane midway along the slot 44. The extremities ofthe posts 45, 46 attached to the broad wall of waveguide segment 43containing slot 44 are the closest together with the posts 45, 46curving outwards so that the remaining extremities are separated morethan at the base. The configuration of the posts 45, 46 is not criticaland may be circular, elliptical, or other curve. Any appropriate meansmay be employed to stiffen the posts 45, 46 and attach them to thewaveguide segment 43.

Referring to FIGS. 5A and 58, there are shown alternate embodiments ofsingle slot radiating elements 50, 51, respectively, each including arectangular waveguide segment 52 with a longitudinal slot 53 in thebroad wall thereof adapted to radiate electromagnetic energy from thewaveguide segment 52. In the case of single slot radiating element 50,posts 54, 55 are attached to the broad walls of rectangular waveguidesegment 52 midway along the longitudinal slot 52 and slant outwards inthe E-plane. The length of the posts 54, 55 is comparable to that of theslot 53. In the case of single slot radiating element 51, FIG. 5B, theposts 54, 55 are made more rigid by incorporating them in taperedchannel structures 56, 57, respectively. The tapered channel structures56, 57 are oriented with the legs of the U in planes parallel to thebroad wall of waveguide 52 facing away from the slot 53.

In FIG. 6 there is shown a top view of a linear array 60 of dipoleaugmented slot radiators in the broad wall of a rectangular waveguide61. In particular, longitudinal slots 6269 are disposed on alternatesides of the centerline in the broad wall of waveguide 61 at one-halfwavelength intervals whereby electromagnetic energy propagated by thewaveguide 61 radiates from the slots 62-69 without additional structureinside thereof. Posts 70, 71; 72, 73; 74, 75; 76, 77; 78, 79; 80, 81;82, 83; and 84, 85 are disposed in the E-plane midway along and onopposite sides of the longitudinal slots 62, 63, 64, 65, 66, 67, 68, 69,respectively, on the exterior of the broad wall of rectangular waveguide61. The posts 7085 are of uniform diameter comparable to the width ofthe slots 62-69 and are spaced a distance substantially equal to adiameter therefrom. The height of the posts 70-85 is of the order ofone-quarter wavelength. One-quarter wavelength elements 86, 87 aredisposed in the E-plane of slot 62 with adjacent extremities on top ofthe posts 70, 71, respectively. Similarly, one-quarter wavelength pairsof elements 88, 89; 90, 91; 92, 93', 94, 95; 96, 97; 98, 99; and 100,101 are disposed in the respective E-planes of slots 63--69 withadjacent extremities thereof directly on top of the posts 72, 73; 74,75; 76, 77; 78, 79; 80, 81; 82, 83; and 84, 85, respectively. Operationof the linear array 61 is conventional, either singly or in conjunctionwith the linear array to form a planar array.

What we claim is:

1. A radiating element comprising a segment of rectangular waveguide ofindeterminate length having a slot capable of radiating microwave energyhaving an E-plane normal to said slot and said waveguide and first andsecond conductive posts disposed in said E-plane midway along and onopposite sides of said slot attached to the exterior side of saidwaveguide thereby to increase the gain ofsaid radiating element.

2. A radiating element comprising a segment of rectangular waveguide ofindeterminate length having a longitudinal slot in a broad wall thereofcapable of radiating microwave energy having an E-plane normal to saidslot and said broad wall and first and second conductive posts disposedin said E-plane midway along and on opposite sides of said longitudinalslot attached to the exterior side of said broad wall thereby toincrease the gain of said radiating element.

3. The radiating element as defined in claim 2 wherein said first andsecond conductive posts slant outwards.

4. The radiating element as defined in claim 2 wherein said first andsecond conductive posts curve outwards.

5. The radiating element as defined in claim 2 wherein said first andsecond conductive posts are vertical cylinders relative to said broadwall with a height substantially equal to onequarter free spacewavelength of said microwave energy.

6. A radiating element comprising a segment of rectangular waveguidehaving a slot capable of radiating microwave energy having an E-planenormal to said slot and said waveguide, first and second cylindricalconductive posts disposed in said E-plane midway along and on oppositesides of said slot and attached vertically to the exterior side of saidwaveguide, said first and second posts having a height substantiallyequal to one-quarter free space wavelength of said microwave frequency,and first and second one-quarter wavelength conductive elements disposedin said E-plane with adjacent extremities thereof on said first andsecond posts, respectively, thereby to increase the gain of saidradiating element.

7. A radiating element comprising a segment of rectangular waveguidehaving a longitudinal slot in a broad wall thereof capable of radiatingmicrowave energy having an E-plane normal to said slot and said broadwall, first and second cylindrical conductive posts disposed in saidE-plane midway along and on opposite sides of said longitudinal slot andattached vertically to the exterior side of said broad wall, said firstand second posts having a height substantially equal to one quarter freespace wavelength of said microwave frequency,

and first and second opeuarter wayclen th conductive elements disposedin said -plane with a acent extremities thereof on said first and secondposts, respectively, thereby to increase the gain of said radiatingelement.

8. The radiating element as defined in claim 7 additionally includingthird and fourth conductive posts of a height substantially equal toone-quarter free spate wavelength disposed over said first and secondposts, in contact with said first and second one-quarter wavelengthelements, respectively; and third and fourth one-quarter wavelengthconductive elements disposed in said E-plane with adjacent extremitiesthereof on said third and fourth posts, respectively.

9. A linear array of radiating elements comprising a rectangularwaveguide of indeterminate length having first and second narrow wallsand first and second broad walls; a plurality of longitudinal slotsdisposed in said first broad wall on alternate sides of the centerlinethereof at uniform intervals, said respective longitudinal slots beingcapable of radiating microwave energy having an E-plane normal theretoand normal to said first broad wall; and means coupled to said microwaveenergy and attached to the exterior side of said first broad wall insaid E-plane midway along and on opposite sides of each of saidplurality of longitudinal slots for increasing the gain ofsaid lineararray.

10. A linear array of radiating elements comprising a rectangularwaveguide having first and second narrow walls and first and secondbroad walls; a plurality of longitudinal slots disposed in said firstbroad wall on alternate sides of the centerline thereof at uniformintervals, said respective longitudinal slots being capable of radiatingmicrowave energy having an E-plane normal thereto and nor mal to saidfirst broad wall; first and second conductive posts disposed on oppositesides of and midway along each of said plurality of longitudinal slots,and first and second one-quarter wavelength elements at the frequency ofsaid microwave energy corresponding to each first and second conductiveposts, respectively, disposed in said E-plane with adjacent extremitieson top thereof.

11. In a planar array of radiating elements, a plurality of segments ofrectangular waveguide disposed in juxtaposition with adjacent segmentshaving common narrow walls; a longitudinal slot in each respective broadwall of said plurality of segments of rectangular waveguide capable ofradiating microwave energy having a common E-plane normal thereto and tosaid broad walls; and a conductive vertical cylinder attached to theexterior side of said broad walls midway along and intermediate eachadjacent pair of said longitudinal slots.

1. A radiating element comprising a segment of rectangular waveguide of indeterminate length having a slot capable of radiating microwave energy having an E-plane normal to said slot and said waveguide and first and second conductive posts disposed in said E-plane midway along and on opposite sides of said slot attached to the exterior side of said waveguide thereby to increase the gain of said radiating element.
 2. A radiating element comprising a segment of rectangular waveguide of indeterminate length having a longitudinal slot in a broad wall thereof capable of radiating microwave energy having an E-plane normal to said slot and said broad wall and first and second conductive posts disposed in said E-plane midway along and on opposite sides of said longitudinal slot attached to the exterior side of said broad wall thereby to increase the gain of said radiating element.
 3. The radiating element as defined in claim 2 wherein said first and second conductive posts slant outwards.
 4. The radiating element as defined in claim 2 wherein said first and seCond conductive posts curve outwards.
 5. The radiating element as defined in claim 2 wherein said first and second conductive posts are vertical cylinders relative to said broad wall with a height substantially equal to one-quarter free space wavelength of said microwave energy.
 6. A radiating element comprising a segment of rectangular waveguide having a slot capable of radiating microwave energy having an E-plane normal to said slot and said waveguide, first and second cylindrical conductive posts disposed in said E-plane midway along and on opposite sides of said slot and attached vertically to the exterior side of said waveguide, said first and second posts having a height substantially equal to one-quarter free space wavelength of said microwave frequency, and first and second one-quarter wavelength conductive elements disposed in said E-plane with adjacent extremities thereof on said first and second posts, respectively, thereby to increase the gain of said radiating element.
 7. A radiating element comprising a segment of rectangular waveguide having a longitudinal slot in a broad wall thereof capable of radiating microwave energy having an E-plane normal to said slot and said broad wall, first and second cylindrical conductive posts disposed in said E-plane midway along and on opposite sides of said longitudinal slot and attached vertically to the exterior side of said broad wall, said first and second posts having a height substantially equal to one-quarter free space wavelength of said microwave frequency, and first and second one-quarter wavelength conductive elements disposed in said E-plane with adjacent extremities thereof on said first and second posts, respectively, thereby to increase the gain of said radiating element.
 8. The radiating element as defined in claim 7 additionally including third and fourth conductive posts of a height substantially equal to one-quarter free space wavelength disposed over said first and second posts, in contact with said first and second one-quarter wavelength elements, respectively; and third and fourth one-quarter wavelength conductive elements disposed in said E-plane with adjacent extremities thereof on said third and fourth posts, respectively.
 9. A linear array of radiating elements comprising a rectangular waveguide of indeterminate length having first and second narrow walls and first and second broad walls; a plurality of longitudinal slots disposed in said first broad wall on alternate sides of the centerline thereof at uniform intervals, said respective longitudinal slots being capable of radiating microwave energy having an E-plane normal thereto and normal to said first broad wall; and means coupled to said microwave energy and attached to the exterior side of said first broad wall in said E-plane midway along and on opposite sides of each of said plurality of longitudinal slots for increasing the gain of said linear array.
 10. A linear array of radiating elements comprising a rectangular waveguide having first and second narrow walls and first and second broad walls; a plurality of longitudinal slots disposed in said first broad wall on alternate sides of the centerline thereof at uniform intervals, said respective longitudinal slots being capable of radiating microwave energy having an E-plane normal thereto and normal to said first broad wall; first and second conductive posts disposed on opposite sides of and midway along each of said plurality of longitudinal slots, and first and second one-quarter wavelength elements at the frequency of said microwave energy corresponding to each first and second conductive posts, respectively, disposed in said E-plane with adjacent extremities on top thereof.
 11. In a planar array of radiating elements, a plurality of segments of rectangular waveguide disposed in juxtaposition with adjacent segments having common narrow walls; a longitudinal slot in each respective broad wall of said plurality of segments of rectangulaR waveguide capable of radiating microwave energy having a common E-plane normal thereto and to said broad walls; and a conductive vertical cylinder attached to the exterior side of said broad walls midway along and intermediate each adjacent pair of said longitudinal slots. 